The goal of iFIT Prosthetics, LLC(r) and its founder was to create and commercialize a modular, immediate fit, fully adjustable, transtibial prosthesis system suitable for mass production using high strength polymer materials that are injection molded at a fraction of the cost of conventionally made prostheses. This goal was achieved and now the aims of this Phase IIB competitive renewal are to; i) complete injection mold manufacture for the remaining sizes of transtibial sockets to make a full line of transtibial prostheses to fit most amputees, ii) develop processes and manufacturing procedures to comply with federal CMS Durable Medical Equipment regulations and FDA Device regulations, iii) complete international standards (ISO 10328) durability testing for all components, iv) develop similar devices for transfemoral amputees, and v) conduct a more rigorous comparative effectiveness study between our devices and conventionally manufactured prostheses. The final design can be fit onto the amputee's residual limb using only a few hand-held tools. Our device is comfortable, light in weight, highly functional, and can be aligned while remaining on the patient. This system is compatible with a large number of commercially available prosthetic feet and silicone pin suspension systems. Our collaboration with Advanced Design Concepts (ADC) and their engineering team has been highly successful in developing this product. The principal business interest in this study iFIT Prosthetics, LLC(r) is well poised to carry out the aims of ths Phase IIB two-year competitive renewal. Commercialization of this American-made, innovative, consumer-centered, cost-effective alternative to the current state of prosthetic fabrication holds great promise to increase access to prosthetic devices and to improve the quality of life for the large and growing number of persons with transtibial and transfemoral amputations domestically and internationally.